1. Field of the Invention
The present invention relates to mounting devices for heat sinks, and particularly to pin-type mounting devices for mounting heat sinks to circuit boards.
2. Related Art
Electronic devices such as central processing units (CPUs) generate a lot of heat during normal operation. This can deteriorate their operational stability and damage associated electronic devices. Thus the heat must be removed quickly to ensure normal operation. A heat dissipation device is often attached to a top surface of a CPU, to remove heat therefrom. Oftentimes, mounting devices are used to mount the heat dissipation device to the CPU.
FIGS. 6–7 show a conventional mounting device mounting a heat sink 6 to a circuit board 9. The mounting device comprises a pin 1 and a spring 2 surrounding the pin 1. The pin 1 comprises a head 3 formed at a top end thereof, and a taper barb 4 formed at a bottom end thereof. An elongate slot 5 is defined in the barb 4 to divide the barb 4 into two halves. The heat sink 6 defines a plurality of first through holes 7. The circuit board 9 defines a plurality of second through holes 7′. In assembly, the heat sink 6 is placed on an electronic component 8 of the circuit board 9 with the first through holes 7 of the heat sink 6 aligned with the second through holes 7′ respectively. The pin 1 extends through the corresponding first and second through holes 7, 7′ in a up-to-down direction. In the process of the pin 1 extending through the second through hole 7′, the two halves of the barb 4 are compressed. After the barb 4 extends through the second through hole 7′, the two halves of the barb 4 return to their original states and abut a bottom surface of the circuit board 9. The spring 2 presses a top surface of the heat sink 6 downwardly and the heat sink 6 is therefore mounted to the heat generating component 8.
However, a large operation force is required to exert on the pin 1 to overcome the elastic force of the barb 4 when the pin 1 is extended through the second through hole 7′. Furthermore, the pin 1 is easy to deflect to wear the heat sink 6 and the circuit board 9 in the through holes 7, 7′ in assembly. The size of the through holes 7, 7′ therefore increases which results in the pin 1 not capable of firmly attaching the heat sink 6 to the circuit board 9.